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A novel alternative to copper bactericide: Magnesium based nanomaterials for management of tomato bacterial spot

Ying-Yu Liao: University of Florida, Department of Plant Pathology

<div>Bacterial spot incited by four <em>Xanthomonas</em> spp., can cause major yield losses of tomato. In Florida, there has been no effective chemical control strategy utilizing bactericides as presence of copper-tolerant strains has rendered Cu-based bactericides ineffective. In addition, EPA has recently posted guidelines suggesting limiting the amount of copper bactericides that can be applied on several vegetable crops. Therefore, finding an effective alternative to copper is very critical. In this study, we demonstrate that a non-formulated magnesium oxide nanoparticles (MgO) have high bactericidal activity against <em>X. perforans</em>. In greenhouse and field experiments, bacterial spot disease severity was significantly reduced by MgO applications at 200 µg/mL compared to the untreated control (UT), whereas the grower standard treatment, copper-mancozeb (K+M), was not significantly different from UT (p = 0.05). In order to determine if nanoparticles accumulated in fruit, inductively coupled plasma mass spectrometry analysis of the fruits from MgO treated plots did not significantly alter levels of Mg, Cu, Ca, K, Mn, P and S compared to fruit in the UT. In our current work, formulated Mg-based nano-materials significantly reduced disease severity to as low as 100 µg/mL compared with Cu+M and UT (p = 0.05) in two greenhouse studies. This demonstrated for the first time antibacterial potential of Mg against <em>X. perforans</em> and its potential use against bacterial spot of tomato.</div>